1. Field of the Invention
The present invention relates to a method of manufacturing an yttria sintered body which has low sintering temperature and excellent plasma-resistance.
2. Description of Prior Art
It is known that an yttria (Y2O3) has excellent plasma-resistance. Also, Patent Document 1-9 and Non-patent Document 1 have proposed that the density and the plasma-resistance of an yttria sintered body (Y2O3) are improved.
Patent Document 1 has proposed that a yttria (Y2O3) powder is formed by a cold isostatic press (CIP), the formed body is fired at 1400-1800° C., cooled, and thereafter heated at 1400-2000° C. in the presence of a boron compound (B2O3), so that a dense yttria (Y2O3) sintered body can be obtained. According to Patent Document 1, it is assumed that the dense sintered body can be obtained because the presence of a boron compound promotes sintering due to diffusion of a B2O3 inside the body.
Patent Document 2 has proposed that Si of 400 ppm or less and Al of 200 ppm or less are contained in an yttria to obtain an yttria sintered body having excellent plasma-resistance.
Patent Document 3 has proposed that Zr, Si, Ce or Al is used as a sintering aid to obtain an yttria sintered body having excellent plasma-resistance whose relative density is 95% or more, which cannot be achieved by a conventional technique.
Patent Documents 4-6 have disclosed that an yttria (Y2O3) sintered body having an excellent transparency and a mechanical strength can be obtained by a HIP treatment after hot pressing of an yttria (Y2O3) powder. Specifically, according to Patent Document 4, a lithium fluoride or a potassium fluoride is added as a sintering aid. According to Patent Document 5, a lanthanoid oxide is added as a sintering aid. According to Patent Document 6, the specific surface area (BET value) of an yttria (Y2O3) powder is adjusted to be 2 m2/g -10 m2/g.
Patent Document 7 has disclosed that Si of 200 ppm or less and Al of 100 ppm or less are contained in an yttria, and that Na, K, Ti, Cr, Fe, and Ni are adjusted to be 200 ppm or less, respectively, which is similar to Patent Document 2.
Patent Document 8 has disclosed that an yttria (Y2O3) green body or an yttria aluminum garnet green body having an excellent plasma-resistance is fired at 1650-2000° C. in a reducing atmosphere.
Patent Document 9 has proposed that a corrosion-resistant ceramic material used for an area to be exposed to plasma comprises an yttrium oxide, an aluminum oxide and a silicon oxide.
Non-patent Document 1 has disclosed that an yttria (Y2O3) powder is formed by a CIP (140 MPa), first sintering is performed to the formed body at 1400-1700° C., BN is sprayed on the sintered body, and second sintering is performed by a HIP (140 MPa, 1400-1700° C.), so that an yttria (Y2O3) sintered body having excellent transparency can be obtained.                Patent Document 1: Japanese Patent Application Publication No. 2000-239065        Patent Document 2: Japanese Patent Application Publication No. 2003-55050        Patent Document 3: Japanese Patent Application Publication No. 2001-181042        Patent Document 4: Japanese Patent Application Publication No. H04-59658        Patent Document 5: Japanese Patent Application Publication No. H04-238864        Patent Document 6: Japanese Patent Application Publication No. H04-74764        Patent Document 7: Japanese Patent Application Publication No. 2002-255647        Patent Document 8: Japanese Patent Application Publication No. 2003-48792        Patent Document 9: Japanese Patent Application Publication No. 2001-31466        Non-patent Document 1: Production of Transparent Yttrium Oxide by HIP sintering, The Ceramic Society of Japan, 2004, Preprint 2G09        
Among these Documents, Patent Document 1 and Non-patent Document 1 disclose the closest technique to the present invention. Hereinafter, the details of Patent Document 1 and Non-patent Document 1 will be described.
Patent Document 1 discloses that heat treatment (HIP) is performed at 1400-2000° C. in the presence of a boron compound such as B2O3. Non-patent Document 1 discloses that a BN is sprayed, and second sintering is performed by a HIP at 1400-1700° C., so as to obtain an yttria (Y2O3) sintered body having a excellent transparency. Patent Document 1 also describes that even if the boron compound is not a B2O3, it is oxidized to be B2O3 by heating in an oxygen atmosphere or by bonding to an oxygen which is present on the surface of the fired body even in a case of heating in a no-oxygen atmosphere.
However, according to these documents, firing at relatively high temperature is required to obtain a sintered body having a small porosity, or a complicated manufacturing process such as a heat treatment in the presence of a boron compound after first sintering or a HIP treatment is required in order to obtain an yttria sintered body.
An object of the present invention is to provide an yttria (Y2O3) sintered body and a corrosion-resistance material having a high density and an excellent plasma-resistance which can be manufactured easily at low temperature, and a manufacturing method thereof.